1. Field of the Invention
This invention relates to an electric vehicle control device, and more particularly to an electric vehicle control device wherein electric motors are driven by PWM converters and inverters.
2. Description of the Related Art
FIG. 5 shows one example of a layout of a conventional electric vehicle control device. In FIG. 5, A.C. power is obtained from an overhead line and is converted by a converter device into D.C. power, which is supplied as drive power to an electric vehicle, and also is supplied to an auxiliary power source device.
This conventional electric vehicle control device consists of: a transformer MT that accepts on its primary side A.C. electric power obtained through a current collector PAN from an A.C. overhead line (not shown), and steps down to voltage of this A.C. power; a rectifier RF that rectifies the secondary output of transformer MT; and a motor control device MCTR and an auxiliary power source device APS connected in parallel with the output side of rectifier RF. Motor control device MCTR controls a motor MM in accordance with a motoring operation command signal p from a motoring operation command circuit MC or in accordance with a brake command signal b from a brake command circuit BS. Auxiliary power source device APS generates drive power of a load LD such as in-carriage air conditioners, illumination devices, and equipment cooling fans etc.
In recent years, electric vehicle control devices have come to be used in which a voltage source pulse width modulation converter (hereinbelow called a PWM converter device) is employed in the portion corresponding to rectifier RF, and a VVVF (variable voltage variable frequency) inverter is employed in the portion corresponding to motor control device MCTR. One example of such electric vehicle control devices has been described in Japanese Patent Disclosure (Kokai) No. Heisei 4-340302 published on Nov. 26, 1992.
However, conventional electric vehicle control devices were subject to the problem that the higher harmonics produced by the switching in the voltage source PWM converter device leaked out into the current of the A.C. overhead line, with considerable adverse effects on the signalling equipments and communications system.
When the effects of such higher harmonics are further considered which is produced by conventional electric vehicle control devices, wherein power is fed from the voltage source PWM converter device to the auxiliary power source device. It suffices to feed power to the vehicle drive motor through the VVVF inverter only during motoring operation or braking operation. However, the auxiliary power source device needs to be fed power uninterruptedly, including during periods of coasting operation. It is therefore necessary to take into consideration the effects of higher harmonics not just during motoring operation and braking operation but also during coasting operation.